WPS: Allow password token to be written with nfcpy

This adds write-password option for the nfcpy example script for
wpa_supplicant to match hostapd wps-ap-nfc.py functionality.

Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>

wpa_supplicant/examples/wps-nfc.py

@@ -54,6 +54,13 @@ def wpas_tag_read(message):
     print wpas.request("WPS_NFC_TAG_READ " + message.encode("hex"))
 
 
+def wpas_get_password_token():
+    wpas = wpas_connect()
+    if (wpas == None):
+        return None
+    return wpas.request("WPS_NFC_TOKEN NDEF").rstrip().decode("hex")
+
+
 def wpas_get_handover_req():
     wpas = wpas_connect()
     if (wpas == None):
@@ -162,6 +169,28 @@ def wps_tag_read(tag):
         time.sleep(0.1)
 
 
+def wps_write_password_tag(clf):
+    print "Write WPS password token"
+    data = wpas_get_password_token()
+    if (data == None):
+        print "Could not get WPS password token from wpa_supplicant"
+        return
+
+    print "Touch an NFC tag"
+    while True:
+        tag = clf.poll()
+        if tag == None:
+            time.sleep(0.1)
+            continue
+        break
+
+    print "Tag found - writing"
+    tag.ndef.message = data
+    print "Done - remove tag"
+    while tag.is_present:
+        time.sleep(0.1)
+
+
 def find_peer(clf):
     while True:
         if nfc.llcp.connected():
@@ -194,6 +223,10 @@ def main():
     clf = nfc.ContactlessFrontend()
 
     try:
+        if len(sys.argv) > 1 and sys.argv[1] == "write-password":
+            wps_write_password_tag(clf)
+            raise SystemExit
+
         while True:
             print "Waiting for a tag or peer to be touched"